The brachialis is a powerful muscle in the upper arm that plays a substantial role in arm size and overall strength. While the biceps brachii often receives the majority of attention in training, the brachialis is arguably the most important elbow flexor for overall arm development. Targeting this muscle specifically is necessary for achieving maximum arm thickness and improving elbow stability. A well-developed brachialis pushes the biceps outward, creating the appearance of a fuller, wider arm.
Anatomy and Primary Function of the Brachialis
The brachialis muscle is situated deep within the upper arm, lying directly beneath the superficial biceps brachii muscle belly. It originates from the anterior surface of the distal half of the humerus, the long bone of the upper arm. The muscle then crosses the elbow joint to insert onto the coronoid process and tuberosity of the ulna, one of the two bones of the forearm.
This muscle is recognized as the prime mover and strongest flexor of the elbow joint, earning it the nickname “the workhorse” of the elbow. Unlike the biceps, which attaches to the radius and assists in forearm rotation (supination), the brachialis attaches only to the ulna. This anatomical difference means the brachialis functions solely to flex the elbow, regardless of forearm position. Studies suggest the brachialis can generate approximately 50% more power during elbow flexion than the biceps alone.
Training Mechanics: How to Isolate the Brachialis
To preferentially target the brachialis muscle over the biceps, specific biomechanical principles related to forearm position must be applied. The biceps brachii is a two-joint muscle, acting as both an elbow flexor and a powerful forearm supinator. The most effective way to reduce the biceps’ contribution and shift the workload to the brachialis is by limiting the biceps’ ability to supinate.
A neutral grip, where the palms face each other, mechanically disadvantages the biceps and increases the activation of the brachialis and the brachioradialis. This grip moves the line of pull away from the biceps’ primary function. Similarly, a pronated grip, with the palms facing downward, further suppresses the biceps’ involvement because the biceps is highly inefficient in this position.
Using a neutral or pronated grip forces the brachialis to handle the majority of the elbow flexion duty. Maintaining strict form, particularly by keeping the upper arm and elbow stable and minimizing momentum, is crucial to ensure tension remains on the brachialis. The movement should be purely a bend at the elbow, avoiding any shoulder movement or excessive wrist flexion. Focusing on a controlled negative (lowering) phase can also enhance the time under tension, providing a strong stimulus for growth in this specific muscle.
Essential Exercises for Brachialis Development
The most direct way to engage the brachialis is by using exercises that employ neutral or pronated grip mechanics.
Hammer Curls
Hammer curls are highly effective because the neutral grip (palms facing each other) minimizes biceps activation, placing a greater emphasis on the brachialis and the brachioradialis. To perform them, hold a dumbbell in each hand with a neutral grip and curl the weights toward your shoulders, keeping your elbows locked at your sides. The focus should be on a smooth, controlled movement, resisting the weight on the way down to maximize muscle fiber recruitment.
Reverse Barbell Curls
Reverse barbell curls utilize a fully pronated grip (palms facing down), which is one of the most effective ways to inhibit the biceps’ supination function. This exercise requires a straight or EZ bar, gripping it with the palms facing the floor, and curling the bar upward while keeping the elbows close to the torso. Because the pronated position also heavily recruits the forearm extensor muscles, a lighter weight than typical bicep curls is necessary to maintain proper form and avoid wrist strain. The movement should be slow and deliberate, focusing on the contraction in the upper forearm and elbow region.
Neutral Grip Cable Curl
The neutral grip cable curl is often performed using a rope attachment. The cable provides constant tension throughout the entire range of motion, unlike free weights where tension can drop. By using a rope, a neutral grip is maintained, and the movement can be performed in a cross-body fashion to increase the peak contraction. This continuous tension is valuable for stimulating muscle growth.
Zottman Curl
The Zottman curl is a hybrid exercise that targets the brachialis during the eccentric (lowering) phase. This movement starts as a standard supinated-grip curl, but at the top of the lift, the wrist is rotated to a pronated grip (palm facing down) before lowering the weight. The controlled descent with the pronated grip forces the brachialis to work hard to resist the load, while the supinated lifting phase ensures comprehensive arm engagement. This combination makes the Zottman curl an efficient way to incorporate brachialis-specific eccentric training into an arm routine.